The Universe Revealed

QPO

QPO

What the heck is QPO? QPO stands for Quasi-periodic oscillation. It's also called Quasi-brightness oscillations. What this is referring to is the way that X-ray frequency of light from an astronomical object oscillates or flutters in brightness around a certain frequency.

Basically, it's seen in X-ray light that's emitted from the inner edge of an accretion disk from objects such as white dwarfs, neutron stars and black holes. When astronomers measure the X-rays emitted from the swirling dust and gas around the accretion discs of these objects, they often see this oscillation in the brightness of the X-ray emissions.

Einstein predicted this effect in his theory of general relativity. He demonstrated with his math that the dust and gas circling around a black hole's event horizon causes an oscillation in time-space, which is reflected in any X-ray emission from the hot gasses that result from friction. This is also called a Hans Thirring precession, which describes a gyroscopic precession of time-space near a large spinning mass. This effect has been shown in Jupiter's polar magnetosphere caused auroras. It's sort of like throwing a pebble into a calm pond.

Essentially, a large rotating mass causes what is known as a frame dragging effect on space-time. The fact is that this effect is happening around Earth, but it's impossible to measure it.
The QPO effect is used to determine the mass of black holes. The larger the mass the stronger the effect. What astronomers are looking at here is the change in power density of the X-ray spectrum from the black hole.

The only problem is the fact that this effect is much lower in the case of black holes compared to neutron stars.

There is no doubt that this effect is real and that it was predicted by Einstein's General Relativity theory. However, it's one of those things in science that's routinely observed but not completely understood.

Thanks for reading.